What C-arm (Computed Radiography) fluoroscopic operational factor results in an increased radiation dose to both the patient and the operating room personnel?

Elevating the Image Receptor Above the Patient's Body is the C-arm Fluoroscopic Factor that Most Increases Radiation Exposure

Elevating the image receptor (intensifier) above the patient's body is the C-arm fluoroscopic operational factor that most significantly increases radiation dose to both the patient and operating room personnel. 1

Mechanism of Increased Radiation Exposure

• Elevating the image receptor above the patient's body can increase the input dose substantially—by as much as a factor of 4 compared to keeping the image receptor close to the patient 1
• Failing to minimize the distance between the patient and the image receptor not only increases entrance port dose to the patient but also increases the scattered radiation dose to the physician operator and other personnel in the room 1
• When the image intensifier is elevated, geometric magnification occurs (air gap technique), which significantly increases radiation output and exposure 1

Comparative Impact on Radiation Dose

• As illustrated in Figure 13 from the ACCF/AHA/HRS/SCAI guidelines, when the image intensifier is elevated while maintaining the same total distance from X-ray tube to detector (110 cm), the skin dose to the patient increases to 260% compared to the optimal positioning 1
• If a procedure performed with optimal positioning required a 3 Gy skin dose, the same procedure with an elevated image intensifier would result in a 7.8 Gy dose 1

Other Factors Affecting Radiation Exposure

While image receptor elevation is the most significant factor, other operational factors also affect radiation exposure:

Exposure Duration

• Beam-on time (fluoroscopy duration) over a single skin entrance site significantly affects total radiation dose 1
• In prolonged procedures, changing fluoroscopy projection angles can help reduce dose to any given area of skin 1

X-ray Tube Positioning

• Placing the X-ray tube too close to the patient's body greatly increases dose to the skin 1
• The distance between the X-ray tube and patient should be maximized when possible 1

Beam Collimation

• Proper collimation (limiting the X-ray field size) reduces scattered radiation within the patient and in the procedure room 1
• Collimation improves image contrast by reducing scattered radiation at the image intensifier 1

Magnification Settings

• Selecting a magnified mode on the image intensifier increases radiation exposure proportionally to the inverse square ratio of the fields of view 1
• The dose is approximately 1.7 times higher in the 7-inch mode compared to the 9-inch mode 1

Patient Factors Affecting Radiation Exposure

• Patient size significantly impacts radiation exposure - larger patients generate more scattered radiation 1, 2
• There is a significant correlation between patient BMI and radiation exposure to the surgical field during fluoroscopy 2

Best Practices to Minimize Radiation Exposure

• Position the X-ray system so that the distance from the patient to the image detector is minimized 1
• Maximize the distance between the X-ray tube and patient when possible 1
• Use the least degree of image magnification required for accurate interpretation 1
• Minimize beam-on time for both fluoroscopy and image acquisition 1
• Use optimal beam collimation to limit X-ray beam size to the minimum area needed 1
• Avoid lateral angulation of the C-arm when possible, as it increases both patient and operator exposure 3

By understanding and controlling these factors, particularly by keeping the image receptor close to the patient, radiation exposure to both patients and operating room personnel can be significantly reduced while maintaining adequate image quality for diagnostic and interventional procedures.